Prior art positioners have generally provided one or two degrees of freedom of linear or rotary motion driven by electromagnetic control. Some electromagnetic positioners have provided three degrees of freedom of movement with a staged system in which two positioners with independent axes are placed one on top of the other and driven by separate or independent actuators/drives. Such staged systems are usually not compact, can produce interference between sensitive electronics, and require the use of air bearings and a mechanism to provide braking or holding torque. They also invariably require multiple actuators, which adds to their bulk and mechanical complexity.
Ultrasonic positioners have been developed which rely on positioning movement by ultrasonic excitation of piezoceramics. The piezoceramics are bonded to an elastic body and produce small movements which drive a moving element placed in preloaded contact with the elastic body, so as to result in linear or rotary motion of the driven element. Ultrasonic positioning systems are capable of micropositioning of mirrors, lenses and cameras where focusing, alignment and tuning are required, as well as other applications. However, they have had some of the same problems as electromagnetic positioners. The conventional ultrasonic positioners are staged to obtain multiple degrees of freedom, and have required multiple, separate actuators.